Conventional infrared sensors, such as they are used in safety engineering, plant technology or in the household appliance industry, measure the temperature of a body from the infrared radiation it emits. Basically, the distinction is made among so-called pyroelectric, bolometric as well as thermoelectric sensors.
It is conventional to produce thermoelectric sensors using thin-film technology, for instance on polyimide foil. Furthermore, micropatterned thermosensors based on silicon technology are also generally conventional.
German Published Patent Application No. 199 32 308 describes manufacturing a thermosensor in the form of a thermal column that is positioned on an at least substantially self-supporting membrane, the thermal contacts of this thermal column being designed to alternate as “hot” and “cold” thermal contacts and being connected to a supporting body by appropriate contact columns, as well as being electrically controllable via these contact columns. German Published Patent Application No. 199 32 308 also describes implementing the thermocouples running on the surface of the substantially self-supporting membrane in the form of circuit traces, which are alternately produced from a first and a second material, so that thermal contacts are created in the region where these two materials come in contact. The first material, in this case, is aluminum, while polysilicon is used as a second material.
German Published Patent Application No. 100 09 593 describes designing a micropatterned thermosensor in the form of an infrared-sensor, for instance, using sacrificial layer technology or some other etching technology, by first creating a thin, self-supporting membrane on a silicon substrate, which is thermally decoupled from a subjacent substrate due to its low thermal conductivity, so that in response to incident infrared radiation, the membrane is warmed more than the substrate. A plurality of micropatterned sensor elements or thermocouples are then situated on the membrane, which thermoelectrically convert a temperature difference between the center of the membrane and the substrate into an electrical signal that is proportional thereto. In accordance with German Published Patent Application No. 100 09 593, the material combinations platinum/polysilicon, aluminum/polysilicon or p-type doped polysilicon/n-type doped silicon are used for the thermocouples created on the self-supporting membrane in the form of circuit traces. The material combination polysilicon/aluminum, which is used primarily in bulk micro-technology, may have the advantage of being CMOS-compatible.
It is conventional that gold, antimony, bismuth and lead tellurides may also be used as materials for thermocouples, with gold also being suitable for bulk micromechanics.
It is an object of the present invention to provide a micropatterned thermosensor having improved sensitivity and stability at higher temperatures than conventional micropatterned thermal sensors.